// Copyright (C) Kumo inc. and its affiliates.
// Author: Jeff.li lijippy@163.com
// All rights reserved.
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published
// by the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.
//
#pragma once

#include <pollux/expression/function_call_to_special_form.h>
#include <pollux/expression/special_form.h>

namespace kumo::pollux::exec {
    constexpr const char *kIf = "if";
    constexpr const char *kSwitch = "switch";

    /// CASE expression:
    ///
    /// case
    ///  when condition then result
    ///  [when ...]
    ///  [else result]
    /// end
    ///
    /// Evaluates each boolean condition from left to right until one is true and
    /// returns the matching result. If no conditions are true, the result from the
    /// ELSE clause is returned if it exists, otherwise null is returned.
    ///
    /// IF expression can be represented as a CASE expression with a single
    /// condition.
    class SwitchExpr : public SpecialForm {
    public:
        /// Inputs are concatenated conditions and results with an optional "else" at
        /// the end, e.g. {condition1, result1, condition2, result2,..else}
        SwitchExpr(
            TypePtr type,
            const std::vector<ExprPtr> &inputs,
            bool inputsSupportFlatNoNullsFastPath);

        void evalSpecialForm(
            const SelectivityVector &rows,
            EvalCtx &context,
            VectorPtr &result) override;

        bool isConditional() const override {
            return true;
        }

        void clearCache() override {
            Expr::clearCache();
            tempValues_.reset();
        }

    private:
        static TypePtr resolveType(const std::vector<TypePtr> &argTypes);

        void computePropagatesNulls() override;

        const size_t numCases_;
        const bool hasElseClause_;
        BufferPtr tempValues_;

        friend class SwitchCallToSpecialForm;
    };

    class SwitchCallToSpecialForm : public FunctionCallToSpecialForm {
    public:
        TypePtr resolveType(const std::vector<TypePtr> &argTypes) override;

        ExprPtr constructSpecialForm(
            const TypePtr &type,
            std::vector<ExprPtr> &&compiledChildren,
            bool trackCpuUsage,
            const core::QueryConfig &config) override;
    };

    class IfCallToSpecialForm : public SwitchCallToSpecialForm {
    public:
        TypePtr resolveType(const std::vector<TypePtr> &argTypes) override;
    };
} // namespace kumo::pollux::exec
